LOS ANGELES--An army of zombie-like attackers keep the teenage protagonists of the "Maze Runner" running for their lives in the second installment of the dystopian young adult film series. In "Maze Runner: The Scorch Trials," out in theaters on Friday, the teens have escaped their maze-like prison from the first film but now face a parched world filled with rebels and antagonists as they race to find a safe haven for themselves. Lead star Dylan O'Brien, who plays franchise hero Thomas, said the characters are caught off-guard by new obstacles thrown their way in this sequel. "Once they're out there, it's strictly survival really, in looking out for one another and sticking together and trying to figure out what's next," O'Brien said. In 2014's "The Maze Runner," based on a young adult sci-fi trilogy of novels by James Dashner, a group of teenage boys and one girl are forced to make their way through a complicated maze filled with lethal creatures. In "Scorch Trials," the survivors face attackers called Cranks, humans who have been infected by a mysterious virus that turns them into the walking dead, which pursue them through a barren wasteland. Rosa Salazar, who plays newcomer rebel Brenda, said the rotting Cranks even managed to startle her. "It shocked me because it's PG-13 and you're like, 'Well how much am I allowed to see?' It's scary. I jumped out of my seat," she said. O'Brien said the film's constant thrills are what will appeal to young audiences. "When I was 12 years old, if I stopped and saw this movie on TV I would have totally watched it and been so into it," he said. "It's cool to be a part of it later because you can tap into your little kid self."